When a males pants are too tight and up their crotch area, causing their balls to visibly split or to bulge to the side of the seam.
Usually visible when they are sitting down.

You're sitting on the train when the man sittin across from you is sitting with his legs open and as you glance up at his crotch area and notice a bulge on both sides of the middle seam. You have just witnessed Camel Balls!

pretty much the same definition for camel toe, but this one goes for a guy who wears his pants so tight that it seperates his balls, one ball being on each side of the seam in his pants below his zipper.